The aims of this proposal will be supported by the unique collection of human mammary cell types available for examination, and the long-term expertise of the groups at LBNL in growth of mammary epithelial cells in both 2D and 3D culture. The ability to examine the Raf-MEK-ERK signaling pathways in normal and transformed cells from one cell type will facilitate these studies by eliminating variables due to differences among cells from differing tissues or organ systems. The cell culture core will ensure that standardized, quality-controlled cell resources are utilized for these studies.